Bearing lubrication device

ABSTRACT

A bearing lubrication device for use in ring-oiled journal bearings and the like in which a generally circular ring member is disposed around the rotatable shaft in the bearing assembly and has a circumferential groove in its inner surface. A cantilevered leaf member projects into the groove in the ring member to separate the lubricant from the ring as rotation occurs, thus providing greater lubricant delivery, improved bearing performance capability, and stabilized performance at high journal speeds.

BACKGROUND OF THE INVENTION

Oil rings are extensively used as conduit means for carrying oil orother lubricant from a reservoir to moving members, such as journalbearings, shafts, and the like. In operation, the oil ring is normallyloosely disposed around the shaft and rotates as the shaft rotates,through contact with the shaft. The lubricant is carried from a sump orreservoir to the shaft, in the contours or grooves of the oil ring andby frictional attraction as the ring moves through the reservoir. Thelubricant is deposited on the shaft or other member through thegravitational, frictional, and centrifugal forces inherent in theoperation. Under conditions of slow rotation, the gravitational andfrictional forces generally deliver a sufficient supply of lubricant;however, at higher velocities, which can be as high as 3000 to 4000ft./min., the oil ring is either moving too fast for gravity to effectdispersion of the oil, or the centrifugal force on the ring and the oilis too great to overcome, and the oil either remains on the ring or isthrown outside of the rotational field. Thus, the lubricant does notreach the desired area, resulting in early wear and possible failure ofthe shaft, bearing, oil ring, or other associated members.

The rotation of the ring depends on a propulsive force developed betweenthe rotating shaft and the ring. As speeds increase, a fluid film isdeveloped, and the driving force is transmitted to the ring by thislubricant film. The situation is analogous in many ways to that in afloating ring bearing and, without a direct drive mechanism, a slippageoccurs. Prior attempts to develop a higher frictional coefficient and,thus, a more positive drive mechanism, have focused on modification ofthe geometry of the inside circumference of the ring. Factors opposingthe ring's rotation are the drag on the lower portion of the ring whichis submerged in the lubricant reservoir, the force required to lift thelubricant from the reservoir toward the top of the journal, and thefrictional drag on the ring applied by close-running stationarysurfaces, such as the sides of the ring slot in the bearing. Otherfactors affecting lubricant delivery include the composition of the ringand the viscosity of the lubricant used in the bearing. In addition,since a conventional oil ring rests on the upper surface of the shaftduring operation and during periods of non-use, much wear results fromthe contact alone. When at rest, most of the lubricant drains back intothe reservoir and very little lubricant protection is available for thestart-up operation. Thus, until the lubricant film is reestablished,early wear of the shaft, ring, bearings, and other associated members islikely to occur. This, in turn, leads to repair and replacementexpenses, and the concomitant loss of operating time.

SUMMARY OF THE INVENTION

It is, therefore, one of the principal objects of the present inventionto enhance the lubricating ability of oil rings, thereby increasing thecapability and the capacity of thrust and journal bearings, by providinga bearing lubrication device having an oil ring and cantilevered oilleaf assembly in which the cantilevered leaf acts to scrape thelubricant from the contours or grooves in the oil ring, directing anddepositing the lubricant in the desired areas around the shaft,bearings, and the ring itself.

Another object of the present invention is to reduce the speed ofrotation of the oil ring, thereby providing increased lubricantdelivery, utilizing the effective braking property provided by theaction of the cantilevered oil leaf against the lubricant flow carriedfrom the reservoir by the ring, and to increase the distribution of thelubricant due to the configuration of the ring and the diverging wedgeconfiguration of the oil leaf.

A further object of the present invention is to provide spring supportto the oil ring, and to prevent the excessive rocking motion whichcharacterizes prior oil ring embodiments by providing a means forminimizing contact between the ring and the shaft, before and duringoperation, thereby minimizing start-up wear of the oil ring, shaft, andbearings, and increasing the useful life of these members.

A still further object of the present invention is to provide an oilring and cantilevered oil leaf assembly which is usable with most or alldevices currently employing conventional oil rings, and which iseconomical to produce and to use.

These and other objects are attained by the present invention whichrelates to a bearing lubrication device for use in ring-oiled journalbearings and the like, which have a rotatable shaft, a bearing surface,and a lubricant reservoir, said device having a generally circular ringmember for carrying lubricant from the reservoir for deposition on theshaft and the bearing surface. The ring member rotates with the shaft,and a means is provided for separating the lubricant from the ring sothat a greater lubricant delivery is attained than was possible withconventional oil rings. For bi-directional journal bearings, a secondlubricant collection means may be added opposite the first means fordirecting the lubricant onto the shaft, bearing surfaces, and into thebearing axis feeder grooves, where present.

Various other objects and advantages of the present invention willbecome apparent from the description below, with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view, shown partially in cross-section, ofa pillow block-type journal bearing assembly with the bearinglubrication device embodying the present invention disposed around theshaft of the bearing assembly;

FIG. 2 is a partial perspective view of the bearing lubrication deviceembodying the present invention, shown here installed in a pillowblock-type bearing, with a portion of the bearing structure broken away,revealing the orientation of the oil ring and cantilevered oil leaf withrespect to the shaft;

FIG. 3 is an enlarged, perspective view, shown partially incross-section, of the oil ring and cantilevered oil leaf embodying thepresent invention, showing the contours of the ring, the section beingtaken from circle 3 of FIG. 2;

FIG. 4 is a partial, schematic and graphical representation of thevarious positions assumed by the cantilevered oil leaf for a shaftrotatable in one direction only;

FIG. 5 is a partial, schematic and graphical representation of analternative embodiment of the present invention, showing the variouspositions assumed by the cantilevered oil leaf on one side of thebearing structure and a separate oil collector leaf opposite thecantilevered leaf, for a shaft rotatable in both directions;

FIG. 6 is a graph of the relationship between the shaft speed and theoil delivery for an oil ring alone, and for an oil ring with acantilevered oil leaf;

FIG. 7 is a graph of the relationship between the shaft speed and theoil delivery for three oil rings, each with a cantilevered oil leaf, therings having various groove depths;

FIG. 8 is a graph of the relationship between the shaft speed, the ringspeed, and the oil delivery for the oil ring alone, which constitutes apart of the present invention;

FIG. 9 is a graph of the relationship between the shaft speed and theoil delivery for three lubricants of different viscosity used with thepresent invention; and

FIG. 10 is a graph of the relationship between the shaft speed and theoil delivery for a shaft rotatable in both directions, for a journalbearing using the oil ring, cantilevered oil leaf, and the oil collectorleaf shown in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now more specifically to the drawings, and to FIG. 1 inparticular, numeral 10 designates generally the bearing lubricationdevice embodying the present invention. The device is shown heredisposed in a journal bearing 12, although its application is notlimited in any way thereto. The assembly can normally be used whereverconventional oil rings are used for lubrication purposes, and in avariety of different devices. In normal operations with bearings of thetype shown, the oil ring 19 is loosely disposed around a rotatable shaft14, and rotates therewith in a manner to be explained below. The oilring rotates in a ring slot 16, through a lubricant reservoir 18 and, asrotation occurs, carries the lubricant upwardly for deposition on theshaft and the bearing surfaces.

FIG. 1 shows a partial cross-section of the oil ring 19 embodying partof the present invention. One of the limiting factors in attaininghigher oil delivery and a stable operating condition with oil rings, isthe configuration of the outer surface. With the present invention, therelative angle of angular sides 20 in conjunction with the length ofvertical sides 22 was found to have the greatest impact on oil delivery,shown here in FIG. 3. As the angle of sides 20 approached zero degrees(0°), the side drag of the ring in ring slot 16 approached the maximumpossible. This caused the ring to operate erratically due to the greaterside drag, and oil delivery was reduced due to insufficient ring speed.As the angle of sides 20 is increased, consequently shortening thelength of sides 22, oil delivery increases accordingly and the lubricantis thrown off the ring by the rotational forces in the form of a splashor spray. Through experimentation, the optimum angle for angular sides20 was found to be approximately thirty degrees (30°), regardless of thediameter of the ring or the depth of the inside groove, here designatedby numeral 24.

At low journal speeds, the oil ring follows the journal and they haveapproximately the same peripheral speed. As the speed of shaft 14increases, a transition point is reached, at which a hydrodynamiclubricant film begins to become established, substantial slippageoccurs, and an appreciable decline in oil ring speed is found. The ringspeed at this transition point is considered to be the primary speed ofthe ring with respect to the journal speed, designated by N₁ in FIG. 8.The relationship at this point is dUr/dUs=O, for Ur=N₁, where N₁ equalsthe oil ring primary speed, Ur equals the surface velocity of the insidediameter of the ring 19, and Us equals the surface velocity of thejournal.

The primary speed of the oil ring is a combined function of ring weight,shape, projected areas of contact, journal speed, lubricant viscosity,and localized temperature. As journal speed increases, thus increasingthe speed of the ring above the primary speed, a hydrodynamic lubricantfilm is definitely established between the ring and the journal. Thepoint where the actual rotating speed of the ring is a balance betweenthe propulsive force at the region of contact between the ring and thejournal, and the resistive force of the lubricant drag on the ring, isdesignated the secondary speed or N₂. This point is also shown in FIG. 8and the relationship is expressed as dUr/dUs=O where Ur=N₂. Thesecondary speed is also a function of many parameters, including journalspeeds, oil viscosity, ring submersion level, and ring shape. Forexample, the greater the length of vertical side 22, the lower thesecondary speed N₂.

Above the secondary speed, lubricant delivery increases very rapidlywith increasing ring speed. Also, as the journal speed continues toincrease, the ring is driven entirely by hydrodynamic action through athicker lubricant film. As more lubricant is drawn from the reservoir,the drag decreases due to the decreased dynamic submersion level of thering in the lubricant reservoir because of the faster rotation. Duringtesting, various rings at a particular shaft speed exhibited anexcessive vibration above the secondary speed N₂. The modes of vibrationcould be readily observed, and they were translatory, conical, andoscillatory modes, where vibration was initiated with an oscillatorymode. The amplitude of the vibration grows as shaft speed increases.This particular ring speed is considered the tertiary speed of the ring,designated as N₃ on FIG. 8. The tertiary ring speed N₃ is believed to bethe first, rigid-body, critical speed of the ring.

As journal speeds increase above the tertiary speed and into theunstable region, the unstable motion of the ring triggers the throw-offof lubricant from both ring and journal. This throw-off and spray becomeso vigorous that lubricant delivery drops rapidly, as shown in FIG. 8.Above the tertiary speed N₃, regardless of journal speed, the rotationalspeed of the ring either remains constant or falls. Several specificfactors influence this tertiary speed, including the ring shape, thering-bore configuration which strongly controls the hydrodynamicstiffness of the ring, the weight or mass of the ring, and the ringdiameter; for example, a larger ring has a lower tertiary speed. Theeffects of changes in lubricant viscosity on ring speed and lubricantdelivery were studied using lubricants of SAE 10, 20, and 30 wt., and itwas found that viscosity affected the primary and secondary speeds ofthe ring; however, tertiary speed was found to be independent ofviscosity.

Various materials may be used in the fabrication of ring 19, includingbrass, Muntz (60% Cu, 40% Zn), and bronze (SEA-660). Tests conducted onthese materials using lubricant SAE 10 at 100° F. and a ring submersionlevel at 15% of the ring diameter, indicated that bronze attained an oildelivery approximately 10% higher than the others tested. Tests of thewear properties, consisting of 30,000 start-stop cycles and 7,200 hoursof continuous running at 1800 rpm, with lubricant SAE 10, indicated lesswear with the brass ring, but differences were slight.

Referring back to FIG. 2, oil ring 19 is shown disposed around shaft 14.The shaft is rotatable in bearing member or liner 40, which may be ofany suitable type and, in the embodiment shown, rotation is in thedirection of the arrow. A means for separating the lubricant from thering or cantilevered oil leaf 42 (C.O.L.) is secured to the liner withsuitable fasteners, such as screws 46. The leaf 42 has a divergingwedge-shaped configuration and is mounted in a unidirectional bearing,such that the direction of rotation of shaft 14 is toward and into thefree end 48 of the leaf. The free end 48 is disposed in the groove 24 ofring 19 and the leaf may be composed of any suitable material, such assteel foil. The design was optimized experimentally, and foil with athickness of approximately 0.5 mm and an arc of approximately 70° wasfound to give optimum performance for any ring and journal combination.The curved foil is preloaded by 10% of the weight of the ring andassumes approximately the position designated by 50A in FIG. 4 when theapparatus is at rest, thereby allowing the outer edges of ring 19 tocontact shaft 14. As rotation of the shaft and ring occurs, lubricant iscarried upwardly from reservoir 18 by inside groove 24 and two outsidegrooves 52 and 54, one on each side of ring 19. The lubricant iscollected and scraped from groove 24 by leaf 42, whereupon the lubricantis deposited on and against the shaft and bearing surfaces. Preloadingof the cantilevered leaf 42 provides spring property which minimizes thecontact between the ring and the shaft, thereby minimizing start-up wearof the elements, and aiding in stabilizing the ring during high speedoperation.

As shown in FIGS. 2 and 4, the rotation of the journal and ring isnormally toward the fixed end of the leaf. Due to the wide configurationof the leaf at the fixed end, the stiffness of the leaf increases fromthe leading edge to the fixed end. This wide structure also serves tocollect the scraped lubricant and direct it to the axial spreader groove(not shown) of the bearing during ring operation. The leading or freeend 48 of the leaf, and its position in groove 24, provide a trackingeffect on the ring, thereby preventing excessive side drag of the ringin ring slot 16. In addition, the free end provides external damping andstiffness to the ring, due to hydrodynamic pressure generation betweenthe leaf and the ring. As ring speed increases with increasing journalspeed, and more lubricant is carried upwardly by the ring, the leaf isforced outwardly, approximately to position 50B in FIG. 4. The outwardmovement thereby produces a diverging wedge configuration, whichprovides, with the hydrodynamic oil pressure generated, a brakingmechanism to the ring, stabilizing it during high speed operation whileincreasing oil delivery. This eliminates the need to machine variousnumbers of grooves in the ring for various journal speeds and sizes. Asjournal speeds increase even further, the divergence effect becomes morepronounced. The ring assumes approximately the position indicated by 50Cin FIG. 4, which is the desired effect, since the more pronounceddivergence produces an even better stabilizing influence and a slowerring speed at higher journal speeds. Thus, stability is inherent athigher ring speeds with an oscillatory motion, due to the divergingwedge configuration.

The effects of varying the depth of groove 24 on lubricant delivery forvarious shaft speeds are plotted in FIG. 7. The three rings tested wereidentical, except for the variance in inside groove depth where groovedepth was D=1.05 mm, D=1.52 mm, and D=3.20 mm. From this data, anoptimum depth of approximately 1.52 mm was selected, providingapproximately twice the oil delivery of rings having shallower or deepergrooves. The ring 19, with an approximate depth of 1.52 mm, wasdesignated ring #5 and was tested with and without the cantilevered oilleaf 42. The results are plotted in FIG. 6. In conducting the test onthe ring without the leaf, instability set in at an approximate journalspeed of 1800 rpm and an approximate ring speed of 180 rpm, and thejournal could be run no higher than approximately 2500 rpm. Ring oildelivery was limited to approximately 1200 cc/min. Testing of the samering with leaf 42 allowed journal operation up to and aboveapproximately 3200 rpm, with an oil delivery of approximately 2100cc/min. at 1800 rpm, and an achievable oil delivery of approximately3200 cc/min. at 1800 rpm, the latter plotted in FIG. 7. Both testsplotted in FIGS. 6 and 7 were run with SAE 20 wt. lubricant. Theincreased oil delivery seen in FIG. 7 can therefore be attributed to ahigher lubricant temperature, which in the test shown in FIG. 7 was48.8° C. at the inlet, whereas in the test shown in FIG. 6, thelubricant temperature was 37.8° C. at the inlet. The effects of variancein lubricant viscosity are plotted in FIG. 9 for lubricants having SAEratings of 10, 20, and 30 weight. As seen, the heavier lubricants showedmarked increases in oil delivery, an important and desirable factor,especially in large bearing applications where the use of heavierlubricants and higher speeds are common.

Where journal bearings have bi-directional capability, an additionalcollector means such as collector leaf 60 is secured to the bearingliner 40 using suitable fasteners such as screws 62, the leaf 60disposed opposite cantilevered leaf 42, shown in FIG. 5. The collectorleaf directs delivered lubricant into the bearing axis feeder groove(not shown), where it is distributed, eventually returning to thereservoir to be picked up by the oil ring and recycled. Oil delivery, asa function of shaft speed for a bi-directional journal bearing, isplotted in FIG. 10 for rotation toward and away from the cantileveredleaf 42, or C.O.L. While a slight drop in oil delivery is observed,delivery is still increased over that for a conventional oil ring alone.Therefore, it is desirable to include the collector 60 in abi-directional bearing, possibly eliminating the need for an externallubrication system. Where the external system is required regardless,due to size of the bearing or other factors, the addition of thecollector is still advisable due to the rapid increase in oil deliveryobserved from the start of operation, thereby minimizing start-up wearof the bearing, shaft, and ring itself.

While one embodiment of a bearing lubrication device and a modificationthereof have been shown and described in detail herein, various otherchanges and modifications may be made without departing from the scopeof the present invention.

I claim:
 1. In combination, a bearing member structure, a rotatableshaft journaled horizontally in said member structure, a lubricantreservoir disposed beneath said shaft, a generally circular ring memberof a substantially larger diameter than said shaft disposedeccentrically around said shaft and supported by the upper side of saidshaft in substantially an area of closest proximity thereto, andextending into said reservoir for transferring lubricant from saidreservoir to the surface of said shaft during rotation thereof, andmeans extending into the ring member to a point near the area of closestproximity between an inner surface of the ring member and said shaft forfacilitating transfer of lubricant from the ring member to the shaftsurface as said ring member is rotated by said shaft.
 2. The combinationas defined in claim 1 in which said means for facilitating transfer ofthe lubricant from said ring member includes a cantilevered leaf memberhaving a generally wedge-shaped configuration with a narrow free end,and a wide fixed end connected to the bearing member structure.
 3. Thecombination as defined in claim 2 in which said ring member has agrooved inner surface for receiving said free end of said cantileveredleaf member, and said cantilevered leaf is mounted such that the shaftnormally rotates toward said free end.
 4. The combination as defined inclaim 3 in which said cantilevered leaf member has a convex outersurface with an arc of approximately seventy degrees for curving aboveand around the shaft.
 5. The combination as defined in claim 1 in whichsaid ring member has a generally flat outer surface and right and leftsides angling away from said outer surface at an approximate thirtydegree angle for a certain defined distance and then angling radiallyinwardly, approximately perpendicular to said outer surface.
 6. Thecombination as defined in claim 5 in which said means for facilitatingtransfer of the lubricant from said ring member includes a cantileveredleaf member having a relatively wide fixed end and a relatively narrowfree end, with said fixed end being secured to the bearing memberstructure.
 7. The combination as defined in claim 6 in which said ringmember has a grooved inner surface with a center groove and two outergrooves, one on each side of said center groove, said surface partiallydefined by said right and left sides for receiving said free end of saidcantilevered leaf member.
 8. The combination as defined in claim 7 inwhich said device includes a lubricant collector leaf disposed oppositesaid cantilevered leaf member and secured to the bearing memberstructure for directing lubricant to a bearing surface.
 9. A bearinglubrication device for use with ring-oiled journal bearings having ahorizontally disposed shaft rotatable in either direction, a bearingstructure with bearing liners for receiving the shaft, and a lubricantreservoir beneath said shaft, said device comprising a generallycircular ring member which is eccentrically supported by the upper sideof said shaft in substantially an area of closest proximity thereto andwhich rotates in the direction of shaft rotation, said ring memberhaving a groove in an inner surface for carrying lubricant from thereservoir to the shaft and bearing liner, and means having a partextending into and parallelling said groove in the inner surface of saidring member at a point near the area of closest proximity between saidring member and said shaft, for separating the lubricant from saidgrooved surface of said ring member and depositing it on the shaftadjacent the bearing liners.
 10. A bearing lubrication device as definedin claim 9 in which said means for separating the lubricant from saidring member includes a cantilevered leaf member having a fixed end and afree end, with said fixed end secured to the bearing structure, and saidfree end includes said part extending into and parallelling said groovein the inner surface of said ring member.
 11. A bearing lubricationdevice as defined in claim 10 in which said ring member has a generallyflat outer surface and right and left sides angling away from said outersurface at an approximate thirty degree angle for a certain defineddistance and then angling downwardly approximately perpendicular to saidouter surface.
 12. A bearing lubrication device as defined in claim 10in which a lubricant collector leaf is disposed opposite saidcantilevered leaf member and secured to the bearing structure fordirecting lubricant to the bearing surface.
 13. A bearing lubricationdevice as defined in claim 10 in which said cantilevered leaf member isyieldable and has an arcuate longitudinal configuration, and said fixedend is relatively wide and said free end is relatively narrow.
 14. Abearing lubrication device as defined in claim 13 in which saidcantilevered leaf member has a convex outer surface with an arc ofapproximately seventy degrees and has a common thickness from said wideend to said narrow end and is composed of steel foil with a thickness ofapproximately 0.5 mm.